K-Meleon's about box and the Netscape bookmarks settings window (Bookmarks --> Config) are independent from the main windows (I don't know about Favorites). You can even close the main window while leaving the about box / bookmarks settings window opened if you run the Loader.
However, unlike the bookmarks settings, the about box does not show up in the taskbar. The only way to access it is by pressing Alt-Tab or by minimizing other windows that get in the way.

Hey, good catch!

I just fixed it for both the bookmarks and the favorites, it's all set for the next release. The about box is a different case that I can't fix myself for various reasons (I'm just the bookmarks guy for now), but I sent an email to the dev list with a heads up. It's a simple problem, so it should be easy to fix.

And while you're at it:
When the about box is closed, it doesn't return focus to the last window opened. In fact, it doesn't return focus to anything, not even the desktop. Hmm....